Hydraulic control device

ABSTRACT

The hydraulic control device for rotating the camshaft of an internal combustion engine has a couple member constructed as a piston (25) connected with the sprocket wheel of the camshaft via a spiral toothing and with the camshaft via a straight toothing. A hydraulic body is mounted on at the camshaft and receives a radial piston pump which delivers the pressure medium required for the displacement of the piston. The pressure space is closed by a controllable pressure limiting valve. An electromagnetic valve controls a pressure medium flow to the piston bores of the radial piston pump and the pressure medium is delivered by an external pump. The sprocket wheel and camshaft are rotated relative to one another by the displacement of the piston.

BACKGROUND OF THE INVENTION

The present invention relates to a hydraulic control device for rotatinga camshaft of an internal combustion engine.

More particularly, it relates to a hydraulic control device for rotatinga camshaft of an internal combustion engine, which has a longitudinallydisplaceable couple member acted upon by pressure and having a firstouter toothing engaging with an inner toothing of a sprocket wheeldriven by the internal combustion engine and a second toothing engaginga toothing of the camshaft, wherein the pressure medium delivered by apump is directed via an electromagnetic valve.

Hydraulic control devices of the above mentioned general type are knownin the art. One of such hydraulic control devices is disclosed in theGerman reference DE-OS 32 47 916.

In such a known control device in particular the pump and theelectromagnetic valve are arranged externally, which is relativelycomplicated, requires a large amount of space, and is very cumbersome inview of the necessary pressure medium connections.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide ahydraulic control device of the above mentioned general type, whichavoids the disadvantages of the prior art.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in a hydraulic control device in which a hydraulic body isflanged on at a widened end portion of the camshaft on which thesprocket wheel also sits, a radial piston pump with a plurality ofpistons slides in approximately radially extending piston bores in thehydraulic body, the spherical caps of the pistons contact an inner ringof a ball bearing which is arranged in a stationary housingeccentrically relative to the axis of the camshaft, an outlet valve isconnected to a pressure space of every piston bore and its outlet opensinto the pressure space of the longitudinal bore hole which receives asingle-action piston and extends in the hydraulic body, the pressurespaces closed by the valve housing of a pressure limiting valvecontrolling the valve housing, and the inlet side of the piston boresare fed by a pump, wherein the magnetic valve which controls the feedflow is arranged between the pump and the piston bores.

When the hydraulic control device is designed in accordance with thepresent invention, it has the advantage over the prior art of a verycompact construction and a very simple installation in the internalcombustion engine or its engine compartment. It operates with highprecision and is also relatively simple to assemble.

In accordance with another feature of the present invention the pressurelimiting valve at the pressure space has a diaphragm which is acted uponby pressure and controls a valve seat constructed at the plate.

The camshaft, the sprocket wheel and the hydraulic body can be connectedby screws which penetrate through sleeves arranged in the sprocket wheelin longitudinal slots, and there are pressure medium connections in thescrews from the piston bores via the electromagnetic valve to the pump.

The electromagnetic valve can be arranged in a bearing member supportingthe camshaft and can receive a tappet connected with the armature so asto actuate the valve member and simultaneously control a connection fromthe pump to the outlet of the electromagnetic valve.

The sensor ring can be arranged on the rotating hydraulic body, athrottle can be provided in the inlet duct to the piston bores. Thetoothing pairs can be formed as a spiral toothing and a spur toothing,wherein the spiral toothing can be formed at the inner circumference ofthe sprocket wheel and the outer circumference of a widened portion ofthe couple member.

Finally, a restoring force can act in form of a pressure spring on thepiston or can be applied by the spiral toothing acting on the piston andhaving an angle of approximately 30°-45°.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section through a hydraulic control devicefor rotating the camshaft of an internal combustion engine;

FIG. 2 shows a section along II--II according to FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 the camshaft which is supported in a camshaft bearing block 11is designated by 10. The sprocket wheel 12 for driving the camshaft 10is arranged at the widened end face 10A of the camshaft 10. A hydraulicbody 13 which receives a radial piston pump 14, which will be discussedbelow, is located next to this sprocket wheel 12. These parts, namelythe hydraulic body 13, sprocket wheel 12 and end part 10A of thecamshaft 10, are connected with one another by a plurality of screws 15.The number of these screws, with one exception, corresponds to thenumber of pistons of the radial piston pump. Slots 16 are constructed inthe sprocket wheel so that the camshaft 10 can rotate relative to thesprocket wheel 12 for the purpose of adjusting the inlet and outletvalves of the internal combustion engine. Sleeves 17 which arepenetrated by the screws 15 are arranged in these slots 16. The slots 16are curved and the sleeves 17 lie therein with a certain amount of play.The screws 15 help to supply the radial piston pump with pressuremedium, but this will be discussed in the following.

The chain wheel 12 has a central bore hole 20 at which a helical orspiral toothing 21 is constructed. The latter meshes with the spiraltoothing 22 at the outer circumference of a widened portion 24 of acouple member 23 which simultaneously forms a piston 25 which can beacted upon by pressure. The couple member is an elongated sleeve fromwhich a cylindrical continuation 27 extends deep into a centrallongitudinal bore hole 28 of the camshaft. A spur or straight toothing29 is formed at the continuation 27 at the height of the camshaftbearing 11 and engages with an identical toothing 30 at the innercircumference of a sleeve 31 which is arranged in the longitudinal borehole 28 so as to be fixed with respect to relative rotation. An annulargroove 32 is situated at the outer circumference of the sleeve 31. Alongitudinal groove 33 proceeds from the outer circumference of theannular groove 32 and a transverse bore hole 34 which penetrates thecamshaft 10 opens into the longitudinal groove 33. The transverse borehole 34 is connected in turn with an annular groove 35 at the outercircumference of the camshaft 10 and lies within the camshaft bearing11. A bore hole 37 which penetrates the camshaft bearing 11 opens intothe annular groove and leads to the shaft 38 of a solenoid valve orelectromagnetic valve 39 where it opens out at an annular groove 40. Theshaft 38 is inserted into a bore hole 41 of the camshaft bearing 11. Theshaft 38 is integral with a pot-shaped housing 43 of the electromagneticvalve 39 which, for the rest, in a conventional manner, has a coil 44and a cylindrical magneto armature 45 in which a tappet 46 is securelyarranged. The tappet 46 dips into a continuous longitudinal bore hole 47in the shaft 38 and cooperates with a valve body 49 which rests againsta valve seat 50 constructed at the longitudinal bore hole 47,specifically due to the force of a pressure spring 51 which is supportedat a sleeve 52 in the longitudinal bore hole. A transverse bore hole 53traversing the shaft 38 penetrates into the annular groove 40. Thetappet has a square 55 at its end facing the valve body. A line 56leading to a pump 57 is connected to the bore hole 41 receiving theelectromagnetic valve 39. The pump 57 sucks pressure medium from an oilreservoir 58 in the internal combustion engine. It should be noted thata pressure spring 60 acts on the armature 45 of the electromagnetagainst the force of the spring 51. Voltage is applied to theelectromagnetic valve 39 at a frequency of approximately 100 Hz with avariable duty factor. At a low duty factor the electromagnetic valve isopened only briefly. The opening cross section averaged over timeincreases with the duty factor.

The radial piston pump 14 has a plurality of radially extending boreholes 62 which are constructed in the hydraulic body. Pistons 63 whosespherical caps contact the inner ring 64 of a ball bearing 65 which iseccentrically arranged in the bore hole 66 of a part of the housing 67of the internal combustion engine slide in these bore holes 62. Adiagonal bore hole 68 which is constructed in the hydraulic bodypenetrates into the central portion of each piston bore 62, a suctionthrottle 69 being arranged in this diagonal bore hole 68. The diagonalbore hole 68 opens out at a transverse bore hole 71 in the screw 15, alongitudinal bore hole 72 opening into this transverse bore hole. Thelatter 72 is connected to a diagonal bore hole 73 in the head part 10Aof the camshaft and opens into the annular groove 32 of the sleeve 31.It will be discerned from this that the piston bores 62 communicate withthe electromagnetic valve 39 and, via the latter, with the pump 57.

A bore hole 75 runs from the base of every piston bore 62 to an outletvalve 76 for the radial piston pump, which is not discussed in moredetail as it involves a conventional construction. A small bore hole 77is arranged at the output of the outlet valve and communicates with apressure space 78 which forms the end portion of a central bore hole 79in the hydraulic body 13. The piston 25 projects into the pressure space78. The piston 25 is acted upon by a pressure spring 80 arranged in itshollow interior. The pressure space 78 is closed by a plate 82 having acentral continuous bore hole 83, an annular valve seat 84 for a valvediaphragm 85 being formed at its rear side. A bore hole 87 penetratesthe plate 82 proceeding from an annular space 86 between the diaphragm85 and the valve seat 84. This bore hole connects with a duct 88 in thehydraulic body, which duct 88 opens into an annular space 89 locatedoutside the hydraulic body. The diaphragm 85 is located in a cover 91closing the plate 84. A duct 92 formed in the cover 91 and connectedwith a throttle bore 93 in the plate 82 proceeds from the rear side ofthe diaphragm. This throttle bore is connected in turn with a duct 94 inthe hydraulic body which leads to a screw 90 as was described above.This screw is arranged in addition to the other screws which areconnected with the piston bores.

The control device operates as follows: when the electromagnetic valve39 is controlled at a low duty factor, only a small amount of pressuremedium flows via the valve 49 into the bore hole 37 and the annularspace 35. The valve body 49 is lifted from the seat only briefly for thepulse period. The pressure medium flows into the bore hole 68 via theduct 34, longitudinal groove 33, annular groove 32, diagonal bore hole73, and bore holes 71, 72 in the screw 15. When the hydraulic body 13rotates, the pistons 63 of the radial piston pump 14 deliver only smallamounts of pressure medium into the pressure space 78 via the outletvalve 76 and the bore hole 77. The diaphragm 85 is likewise pressed onthe valve seat 84 with only slight force. The pressure medium requiredfor this likewise flows via the bore holes in the screw 90, the duct 94,the throttle 93 and the duct 92 behind the diaphragm 85. However, theforce of the spring 80 acting on the piston 25 is greater than thepressure force of the pressure medium in the space 78 so that thediaphragm 85 which contacts the valve seat with a slight force is liftedand the pressure medium can flow off via the annular space 86 and duct87, 88. The pressure spring 80 now displaces the couple member in thedirection of the plate 82. A relative rotation of the sprocket wheel 12relative to the camshaft 10 is now effected by the toothing 29, 30 and21, 22 at the collar 24 and the sleeve 31, respectively. The camshaftnow occupies a first position.

When the electromagnetic valve 39 is supplied with current at a highduty factor with a corresponding opening of same averaged over time, agreater amount of pressure medium arrives in the piston bores 62 so thatthe radial piston pump 14 delivers a proportionately greater amount.This also substantially increases the pressure in the pressure space 78and the diaphragm 85 is also pressed onto the valve seat 84 with greaterforce via the duct connection described above so that pressure mediumcan no longer flow out of the pressure space 78. The piston 25 is nowmoved against the force of the spring 80 and the couple member 23provided with the above-mentioned toothing now rotates the camshaft 10relative to the sprocket wheel 12 in an opposite direction as before, sothat the inlet and outlet valves of the internal combustion engineoccupy a second position. As a result of corresponding partialapplication of current to the electromagnetic valve 39, the pressureforce on the piston 25 can be maintained in equilibrium with the forceof the spring 80 and the axial force due to the spiral toothing and adetermined center position or any other desired position is achieved.

A sensor ring 96 is also securely arranged on the hydraulic body 13 androtates with it. It has a toothing, not shown, at the diagonal in aworking connection with a suitable sensor. The electromagnetic valve 39is controlled by the sensor and an electronic device which is not shownin the drawing.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in ahydraulic control device, it is not intended to be limited to thedetails shown, since various modifications and structural changes may bemade without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present inveniton that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:
 1. A hydraulic control device for rotating a camshaft of aninternal combustion engine, comprising a sprocket wheel which is drivenby an internal combustion engine and having an inner circumferenceprovided with a toothing; a longitudinally displaceable couple memberwhich is acted upon by a pressure and having a first toothing providedat a first location of its outer circumference and engaging with saidtoothing at said inner circumference of said sprocket wheel and alsohaving a second toothing provided at an other location of its outercircumference and engaging with a toothing of a camshaft, so as to formtwo toothing pairs, one of said toothing pairs being formed as a spiraltoothing while another of said toothing pairs being formed as a straighttoothing; a single acting piston which is acted upon by a pressuremedium against a mechanical force and is arranged at said couple member;a pump and an electromagnetic valve arranged so that a pressure mediumis delivered by said pump and directed via said electromagnetic valvefor application of pressure on said piston, said sprocket wheel beingrotated relative to the camshaft by a displacement of said couplemember; a hydraulic body mountable at a widened end portion of thecamshaft on which said sprocket wheel also sits and having substantiallyradially extending piston bores, said hydraulic body having alongitudinal bore hole a radial piston pump having a plurality ofpistons sliding in said piston bores of said hydraulic body; a ballbearing arranged eccentrically relative to an axis of the camshaft andhaving an inner ring contacted by said pistons; an outlet valveconnected to a pressure space of each of said piston bores and having anoutlet, said single acting single-action piston being received in saidlongitudinal bore hole of said hydraulic body, said outlet of saidoutlet valve opening into a pressure space of said longitudinal borehole; a pressure limiting valve having a valve housing and controllingthe pressure space of said longitudinal bore hole, said valve housingclosing said pressure space, said pump feeding inlet sides of saidpiston bores, and said electromagnetic valve controlling a feed flow andbeing arranged between said pump and said piston bores.
 2. A hydrauliccontrol device as defined in claim 1, wherein said pistons havespherical caps which contact said inner ring of said ball bearing; andfurther comprising a stationary housing in which said ball bearing isarranged.
 3. A hydraulic control device as defined in claim 1, whereinsaid pressure limiting valve has a plate, a valve seat formed at saidplate, and a diaphragm which is acted upon by pressure and controllingsaid valve seat.
 4. A hydraulic control device as defined in claim 1,wherein said sprocket wheel has longitudinal slots and sleeves arrangedin said longitudinal slots; and further comprising means for connectingsaid camshaft, said sprocket wheel and said hydraulic body and includingscrews which penetrate through said sleeves.
 5. A hydraulic controldevice as defined in claim 4, and further comprising pressure-mediumconnections arranged in said screws and extending from said piston boresvia said electromagnetic valve to said pump.
 6. A hydraulic controldevice as defined in claim 1, and further comprising a bearing memberarranged to support the camshaft, said electromagnetic valve having avalve member, an armature, and a tappet which is received in saidbearing member, connected with said armature and actuates said valvemember, said tappet simultaneously controlling a connection from saidpump to an outlet of said electromagnetic valve.
 7. A hydraulic controldevice as defined in claim 1, and further comprising a sensor ringarranged on said hydraulic body.
 8. A hydraulic control device asdefined in claim 1, and further comprising means forming an inlet ductto said piston bores; and a throttle arranged in said inlet duct.
 9. Ahydraulic control device as defined in claim 1, wherein said spiraltoothing ia formed at the inner circumference of the sprocket wheel andat the outer circumference of a widened portion of said couple member.10. A hydraulic control device as defined in claim 1, and furthercomprising a pressure spring providing a restoring force which acts onsaid piston.
 11. A hydraulic control device as defined in claim 1,wherein said spiral toothing is arranged so that it applies a restoringforce acting on said piston.
 12. A hydraulic control device as definedin claim 11, wherein said spiral toothing has an angle of substantially30°-45°.